Arc welding method and arc welding device

Abstract

To suppress spatter from being generated when releasing a short-circuit.SOLUTION: An arc-welding device performs welding while alternately repeating a short-circuit period during which a short-circuit state in which a welding wire and a base material are short-circuited occurs and an arc-period during which an arc state where an arc occurs in a space between the welding wire and the base material occurs. A calculating part calculates electric power integrated values by integrating electric power supplied to the welding wire within a predetermined period of time, after the welding wire is short-circuited. A control part decreases welding electric currents that are supplied to the welding wire, when the electric power integrated values are larger than a predetermined threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an arc welding method and an arc welding apparatus. [Background technology]

[0002] Patent Document 1 discloses a control method for an arc welding device that calculates the amount of change in welding voltage per predetermined time and determines whether a droplet is constricted based on the amount of change in welding voltage per predetermined time and a droplet constriction determination threshold.

[0003] Specifically, when a constriction (a so-called neck) occurs between the welding wire and the base metal fusion zone, the cross-sectional area of ​​the neck decreases, causing an increase in resistance. Therefore, when a neck occurs, the amount of change in welding voltage increases, even though the current increase is kept constant through short-circuit control. Therefore, when the occurrence of a neck is detected based on the amount of voltage change, the welding current is reduced just before the short circuit is released, thereby suppressing the generation of spatter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4760053 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when using a welding wire with low resistance, such as copper or aluminum, even if a constriction occurs, the change in welding voltage caused by the constriction is small and there is also a large variation, so there is a risk of incorrectly determining whether or not a constriction exists.

[0006] For example, if it is erroneously determined that there is no constriction when there is, short-circuit welding will continue without reducing the welding current, which will increase the amount of heat input when the short circuit is released, resulting in the problem of spatter.

[0007] The present invention has been made in view of the above points, and its object is to suppress the generation of spatter when a short circuit is opened. [Means for solving the problem]

[0008] A first invention is directed to an arc welding method that alternates between a short-circuit period in which a short circuit state occurs between a welding wire and a base metal and an arc period in which an arc occurs between the welding wire and the base metal. The arc welding method includes a step of integrating power supplied to the welding wire within a predetermined period after the welding wire is short-circuited to calculate an integrated power value, and a step of reducing a welding current supplied to the welding wire when the integrated power value is greater than a predetermined threshold during the short-circuit period.

[0009] In the first aspect of the present invention, an integrated power value within a predetermined period after a welding wire is short-circuited is calculated, and if the integrated power value is greater than a predetermined threshold, the welding current is reduced.

[0010] In this way, the welding current is reduced based on the integrated amount of power supplied to the welding wire before the short circuit is opened, thereby reducing the amount of heat input to the welding wire, thereby suppressing the generation of spatter when the short circuit is opened.

[0011] Furthermore, since the welding current is reduced before the short circuit is opened without detecting the occurrence of a constriction, problems caused by erroneous determination of the presence or absence of a constriction can be avoided.

[0012] In a second aspect of the present invention, in the first aspect of the present invention, in the step of calculating the integrated power value, calculation of the integrated power value starts after a predetermined time has elapsed since the welding wire is short-circuited.

[0013] In the second aspect of the present invention, calculation of the integrated power value is started after a predetermined time has elapsed since the welding wire was short-circuited, for example, after the short circuit has stabilized, thereby making it possible to calculate the integrated power value while excluding the period during which the short circuit is not stable.

[0014] A third invention is the first or second invention, wherein in the step of calculating the integrated power value, calculation of the integrated power value starts after the welding current starts to increase after the welding wire is short-circuited.

[0015] In the third aspect of the present invention, calculation of the integrated power value is started after the welding current starts to increase after the welding wire is short-circuited, so that an appropriate amount of heat can be applied to the welding wire even if there is a change in the welding voltage.

[0016] A fourth invention, in any one of the first to third inventions, further includes a step of feeding the welding wire in reverse after the welding current starts to increase after the welding wire is short-circuited, or after a predetermined time has elapsed since the short-circuit.

[0017] In the fourth aspect of the present invention, the welding wire is fed in reverse after the welding current starts to increase after the welding wire is short-circuited, or after a predetermined time has elapsed since the short-circuit occurred, thereby preventing the welding wire from buckling.

[0018] The fifth invention may further include a step of determining whether the integrated power value is greater than a predetermined threshold value. The predetermined threshold value may be a fixed value. Furthermore, the fixed value may be determined for each welding condition.

[0019] A sixth aspect of the present invention is directed to an arc welding device that performs welding that alternately includes a short circuit period in which a short circuit state occurs between a welding wire and a base metal and an arc period in which an arc occurs between the welding wire and the base metal, and includes a calculation unit that calculates an integrated power value by integrating power supplied to the welding wire within a predetermined period after the welding wire is short-circuited, and a control unit that reduces the welding current supplied to the welding wire when the integrated power value is greater than a predetermined threshold during the short circuit period.

[0020] In a sixth aspect of the present invention, the calculation unit calculates an integrated power value within a predetermined period after the welding wire is short-circuited, and the control unit reduces the welding current when the integrated power value is greater than a predetermined threshold.

[0021] In this way, the welding current is reduced based on the integrated amount of power supplied to the welding wire before the short circuit is opened, thereby reducing the amount of heat input to the welding wire, thereby suppressing the generation of spatter when the short circuit is opened.

[0022] A seventh aspect of the present invention includes a plurality of arc welding devices according to the sixth aspect of the present invention, and the ground side cables of the plurality of arc welding devices are connected to the base material, respectively.

[0023] In a seventh aspect of the present invention, the ground side cables of a plurality of arc welding devices are connected to the base material, and the plurality of arc welding devices reduce the welding current when opening a short circuit based on the integrated value of the power supplied to the welding wire, i.e., the amount of heat actually input to the welding wire.

[0024] Therefore, even if the influence of noise generated in one arc welding device extends to the other arc welding device via the base material, or if the welding wire is made of a low-resistance material containing aluminum or copper and therefore the voltage change is small, making it impossible to accurately detect the voltage and therefore impossible to accurately determine the presence of a neck, it is possible to reliably control the welding current to be reduced before the short circuit between the welding wire and the base material is opened based on the integrated power value.

[0025] In an eighth aspect of the present invention, in the sixth aspect, the control unit may further determine whether the integrated power value is greater than a predetermined threshold value. The predetermined threshold value may be a fixed value. Furthermore, the fixed value may be determined for each welding condition. [Effects of the Invention]

[0026] According to the present invention, it is possible to suppress the occurrence of spatter when a short circuit is opened. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a block diagram showing a schematic configuration of an arc welding device according to an embodiment; [Figure 2] 4A and 4B are diagrams showing output waveforms of a welding voltage, a welding current, and an integrated power value during arc welding. [Figure 3] 10A and 10B are diagrams illustrating output waveforms of integrated current values ​​and integrated power values. [Figure 4] FIG. 10 is a block diagram showing a schematic configuration of an arc welding apparatus according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

[0029] As shown in FIG. 1, arc welding apparatus 10 performs welding that alternately includes short-circuit periods in which a short circuit state occurs between welding wire 34, which is a consumable electrode, and base metal 35, which is an object to be welded, and arc periods in which an arc occurs between welding wire 34 and base metal 35.

[0030] The arc welding device 10 has a first rectifier unit 11, a first switching unit 12, a transformer 13, a second rectifier unit 14, a second switching unit 15, a resistor 16, a reactor 17, a welding current detection unit 18, a welding voltage detection unit 19, and a control unit 20.

[0031] First rectifier 11 rectifies the input voltage input from input power source S external to arc welding apparatus 10. First switching unit 12 adjusts the output of first rectifier 11 by switching operation. Transformer 13 converts the output of first switching unit 12 into an output suitable for welding.

[0032] The second rectifier 14 rectifies the output of the transformer 13. The second switching unit 15 adjusts the output of the second rectifier 14 by switching operation. The resistor 16 is connected in parallel with the second switching unit 15.

[0033] The reactor 17 is connected in series with the second switching unit 15. The reactor 17 smoothes the output of the second switching unit 15.

[0034] The welding current detection unit 18 detects the welding current supplied between the welding wire 34 and the base material 35. A detection signal indicating the welding current detected by the welding current detection unit 18 is transmitted to the control unit 20.

[0035] The welding voltage detection unit 19 detects the welding voltage supplied between the welding wire 34 and the base material 35. A detection signal indicating the welding voltage detected by the welding voltage detection unit 19 is sent to the control unit 20.

[0036] Arc welding apparatus 10 is connected to welding torch 30, base material 35, wire feeder 32, and setting unit 25 to form an arc welding system.

[0037] Welding torch 30 is provided with a welding tip 31 for supplying power to welding wire 34. Based on a signal from control unit 20, wire feeder 32 controls the feeding of welding wire 34, such as constant feed control at a predetermined feed speed or forward and reverse feed control, which alternates between forward feed, in which welding wire 34 is fed in the direction of base material 35, and reverse feed, in which welding wire 34 is fed in the opposite direction to the forward feed.

[0038] When controlling the feed of forward and reverse feed, welding is performed by alternately feeding the welding wire 34 in forward and reverse directions, and alternately generating a short circuit state and an arc state. Forward and reverse feed are performed periodically to mechanically alternately generate a short circuit state and an arc state.

[0039] It is also possible to switch between forward and reverse feeding depending on the state of the welding phenomenon, rather than periodically switching between forward and reverse feeding. Specifically, when welding wire 34 is short-circuited with base metal 35, the welding wire 34 is fed in reverse, and when the short circuit is released and an arc is formed, the welding wire 34 is fed in forward.

[0040] The setting unit 25 is used to set welding conditions for the arc welding device 10.

[0041] The welding output of the arc welding device 10 is supplied to the welding wire 34 via the welding tip 31. Then, the welding output of the arc welding device 10 generates an arc 36 between the welding wire 34 and the base material 35, thereby performing welding.

[0042] Control unit 20 transmits signals between each unit of arc welding apparatus 10 and devices external to arc welding apparatus 10. In the example shown in Fig. 1, the units of arc welding apparatus 10 are first switching unit 12, second switching unit 15, welding current detection unit 18, and welding voltage detection unit 19. In addition, the devices external to arc welding apparatus 10 are wire feeder 32 and setting unit 25.

[0043] Control unit 20 controls the welding output by outputting a control signal to first switching unit 12 and second switching unit 15. Control unit 20 outputs a control signal to wire feeder 32 to control the wire feed speed.

[0044] The control unit 20 includes a processor and a memory electrically connected to the processor for storing programs and information for operating the processor.

[0045] The calculation unit 21 calculates the integrated power value by integrating the power supplied to the welding wire 34 within a predetermined period after the welding wire 34 is short-circuited. The power supplied to the welding wire is calculated based on the product of the welding current and the welding voltage.

[0046] Control unit 20 compares the welding voltage detected by welding voltage detection unit 19 with a preset threshold voltage. If the welding voltage is equal to or less than the threshold voltage, it determines that a short circuit has occurred. On the other hand, if the welding voltage exceeds the threshold voltage, it determines that an arc has occurred.

[0047] The control of the welding current by the control unit 20 will be described below.

[0048] 2, when it is determined at time t1 that a short circuit has occurred, control unit 20 reduces the welding current to the initial current by adjusting the output of first switching unit 12. At this time, second switching unit 15 remains in the conductive state.

[0049] Thereafter, the control unit 20 adjusts the output of the first switching unit 12 so that the welding current increases at a predetermined current increase rate from time t2 to time t3. At this time, the control unit 20 controls the operation of the wire feeder 32 to feed the welding wire 34 in the reverse direction. Alternatively, the welding wire 34 may be fed in the reverse direction after a predetermined time has elapsed since the short circuit occurred (after the short circuit has stabilized). By feeding the welding wire in the reverse direction during the short circuit, it is possible to promote the release of the short circuit between the welding wire 34 and the base metal 35. In particular, by controlling the forward and reverse feed of the welding wire 34 by periodically switching between the forward and reverse feeds, droplet formation at the tip end of the welding wire 34 becomes more stable, and the stability of droplet transfer from the welding wire 34 to the base metal 35 is improved.

[0050] It is not necessary to control the forward and reverse feeding of the welding wire 34. For example, the welding wire 34 may be fed at a constant rate without being fed in reverse.

[0051] Calculation unit 21 calculates the integrated power value by integrating power between time t2 and time t4. Specifically, calculation of the integrated power value starts after the welding current starts to increase after welding wire 34 is short-circuited. For example, calculation unit 21 detects the increase in welding current and, in response, starts calculating the integrated power value. Alternatively, calculation unit 21 detects the passage of time during which the welding current is expected to increase and, in response, starts calculating the integrated power value.

[0052] The calculation of the integrated power value may be started after a predetermined time has elapsed since the welding wire 34 was short-circuited, for example, after the short circuit has stabilized. For example, the calculation of the integrated power value may be started between time t1 and time t2. The calculation unit 21 may detect the passage of the predetermined time and start calculating the integrated power value in response to the detection.

[0053] The control unit 20 determines whether the integrated power value is greater than a predetermined threshold value P. In the example shown in FIG. 2, the integrated power value is greater than the threshold value P at time t3. When the integrated power value is greater than the predetermined threshold value P, the control unit 20 switches the second switching unit 15 from the conductive state to the cut-off state, thereby reducing the welding current supplied to the welding wire 34.

[0054] At time t4, the opening of the short circuit between welding wire 34 and base material 35 is detected. Control unit 20 adjusts the output of first switching unit 12 so that the welding current becomes a predetermined current. At this time, second switching unit 15 remains in the conductive state. Then, at time t4, the short circuit is opened and the state transitions to an arc state.

[0055] Here, when the integrated power value exceeds the threshold P during the short circuit period, the integrated power value is reset and the integration is terminated. If the integrated power value does not exceed the threshold P, the integrated power value is reset and the integration is terminated by the arc determination that an arc state exists.

[0056] As described above, in the arc welding device 10 according to this embodiment, the welding current is reduced before opening the short circuit based on the integrated amount of power supplied to the welding wire 34, thereby reducing the amount of heat input to the welding wire 34. This makes it possible to suppress the generation of spatter when opening the short circuit.

[0057] <Comparison of current integrated value and power integrated value> Hereinafter, it was examined whether similar control can be performed even when an integrated current value obtained by integrating the welding current is used instead of the integrated power value.

[0058] 3, the integrated current value shows three peak values ​​P1, P2, and P3. Therefore, for example, if P1, which is the largest integrated current value, is set as a threshold value, when the integrated current value is P2 or P3, it is below threshold value P1. Therefore, the control unit 20 does not reduce the welding current supplied to the welding wire 34 at the times when the integrated current value is P2 or P3.

[0059] However, when the peak value of the integrated power value is observed at the times when the integrated current value reaches P2 and P3, the integrated power value is greater than the threshold value P. Therefore, if short-circuit welding is continued without reducing the welding current at the times when the integrated current value reaches P2 and P3, the heat input when the short circuit is opened will be large, resulting in spatter.

[0060] On the other hand, if P3, the smallest current accumulated value, is used as the threshold, the control unit 20 will reduce the welding current at a time when there is no need to reduce the heat input, before the current accumulated value reaches P1 or P2, resulting in variation in the heat input.

[0061] From the above study results, it can be seen that determining the timing to reduce the welding current supplied to the welding wire 34 based on the integrated power value is more effective in reducing the welding current at the timing to reduce the heat input than determining the timing based on the integrated current value, making the heat input during the short circuit period more stable and being advantageous in suppressing the generation of spatter when the short circuit is opened.

[0062] "Variations" As shown in Fig. 4, a plurality of arc welding devices 10 are provided (two in the example shown in Fig. 4). The ground side cables of the two arc welding devices 10 are connected to one base material 35. Specifically, welding is performed by the plurality of arc welding devices 10 on a common base material 35 that is electrically connected, or on a base material 35 on a common jig (not shown). In this way, arcs 36 are generated simultaneously from the two arc welding devices 10.

[0063] Here, in the arc welding device 10 of this embodiment, the welding current when the short circuit is opened is reduced based on the integrated value of the power supplied to the welding wire 34, that is, the amount of heat actually input to the welding wire 34.

[0064] Therefore, even if the influence of noise generated in one arc welding device 10 for other welding extends to the other arc welding device 10 via the base material 35, or even if the welding wire 34 is made of a low-resistance material containing aluminum or copper and therefore the voltage change is small, making it impossible to accurately detect the voltage and therefore making it impossible to accurately determine the presence of a neck, it is possible to reliably control the welding current to be reduced before the short circuit between the welding wire 34 and the base material 35 is opened based on the integrated power value. [Industrial Applicability]

[0065] As described above, the present invention has a highly practical effect of suppressing the generation of spatter when a short circuit is opened, and is therefore extremely useful and has high industrial applicability. [Explanation of symbols]

[0066] 10. Arc welding equipment 20 Control Unit 21 Calculation section 32 Wire feeder 34 Welding wire 35 Base material

Claims

1. An arc welding method including alternately and repeatedly a short circuit period in which a short circuit state occurs in which a welding wire is short-circuited to a base metal and an arc period in which an arc state occurs in which an arc is generated between the welding wire and the base metal, a step of calculating an integrated power value by integrating power supplied to the welding wire within a predetermined period after the welding wire is short-circuited; and reducing a welding current supplied to the welding wire when the integrated power value is greater than a predetermined threshold during the short circuit period.

2. In claim 1, In the step of calculating the integrated power value, calculation of the integrated power value is started after a predetermined time has elapsed since the welding wire was short-circuited.

3. In claim 1 or 2, In the step of calculating the integrated power value, calculation of the integrated power value is started after the welding current starts to increase after the welding wire is short-circuited.

4. In any one of claims 1 to 3, an arc welding method comprising a step of feeding the welding wire in reverse after the welding current starts to increase after the welding wire is short-circuited, or after a predetermined time has elapsed since the short-circuit.

5. 2. The method of claim 1, further comprising determining whether the power accumulation value is greater than the predetermined threshold value, The arc welding method, wherein the predetermined threshold value is a fixed value.

6. 1. An arc welding device that performs welding that alternately and repeatedly includes a short circuit period in which a short circuit state occurs in which a welding wire is short-circuited to a base metal and an arc period in which an arc state occurs between the welding wire and the base metal, a calculation unit that calculates an integrated power value by integrating power supplied to the welding wire within a predetermined period after the welding wire is short-circuited; and a control unit that reduces a welding current supplied to the welding wire when the integrated power value is greater than a predetermined threshold during the short circuit period.

7. A plurality of the arc welding devices according to claim 6 are provided, The arc welding devices have ground side cables connected to the base material, respectively.

8. 7. The method according to claim 6, wherein the control unit further determines whether the integrated power value is greater than the predetermined threshold value; The predetermined threshold value is a fixed value.

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